This combination IC integrates power factor correction (PFC) and quasi-resonant flyback functionality necessary to implement a compact and highly efficient Switched Mode Power Supply for an adapter application.
The PFC stage exhibits near-unity power factor while operating in a Critical Conduction Mode (CrM) with a maximum frequency clamp.The circuit incorporates all the features necessary for building a robust and compact PFC stage while minimizing the number of external components.
The quasi-resonant current-mode flyback stage features a proprietary valley-lockout circuitry, ensuring stable valley switching.This system works down to the 4th valley and toggles to a frequency foldback mode with a minimum frequency clamp beyond the 4th valley to eliminate audible noise. Skip mode operation allows excellent efficiency in light load conditions while consuming very low standby power consumption.

• High Voltage Startup Circuit and Active Input Filter Capacitor Discharge Circuitry
• High Voltage Line Voltage Detector
• Integrated High Voltage Switch Disconnects PFC Feedback Resistor Divider
• Fault Input for Severe Fault Conditions
• Bi-Level Line-Dependent Output Voltage
• Boost Diode Short-Circuit Protection
• Adjustable PFC Disable Threshold Based on Output Power
• Frequency Foldback with Minimum Frequency Clamp
• Minimum Frequency Clamp
• Valley Switching Operation with Valley-Lockout